ed on mon 19 mar 01
WHAT CONE FOR OPAL BLUE VARIATIONS????????
-----Original Message-----
From: Cindy Strnad
To: CLAYART@LSV.CERAMICS.ORG
Date: Sunday, March 18, 2001 7:08 AM
Subject: Opal Blue Variations
>Hi, Guys.
>
>Well, I just unloaded a bunch of cool glaze tests, so I thought I'd share
>them with you. The first group of tests were done using the Opal Blue
base,
>which follows:
>
>EPK KAOLIN.......... 25.00 25.00%
> FRIT 3134........... 50.00 50.00%
> SILICA.............. 25.00 25.00%
> ========
> 100.00
>
> CaO 0.68* 10.46%
> MgO 0.00* 0.03%
> K2O 0.00* 0.09%
> Na2O 0.31* 5.35%
> TiO2 0.00 0.10%
> Al2O3 0.35 9.78%
> B2O3 0.63 11.97%
> P2O5 0.00 0.06%
> SiO2 3.76 61.96%
> Fe2O3 0.00 0.21%
>
> Cost/kg 2.49
> Si:Al 10.75
> SiB:Al 12.54
> Expan 6.84
>
>These figures are the standard figures in the Material Data Table provided
>with Insight.
>
>Normally, I'd add:
>Cobalt Oxide 2%
>Rutile 4%
>
>For a rich, deep, mottled blue.
>
>However, at Chris Shafale's suggestion, I tried the following:
>
>Cobalt Carb 1%
>Red Iron Oxide 2% (RIO)
>Rutile 4%
>
>and got the same texture, with a rather more muted-greenish blue. Very
>attractive, just different.
>
>Then I tried:
>Cobalt Carb 1.25%
>RIO 2.00%
>Rutile 4.50%
>
>and got a slightly paler blue, more green. Also nice.
>
>I also tried, instead of the other colorants:
>
>RIO 7% and 10%
>
>and got, respectively, a deep, rich, translucent, very glossy brown with
>some gold flecks along the rim, and the same brown with large, lighter,
>reddish areas. I really liked the 10% iron test.
>
>I want to try this with a prodigious amount of iron next (like maybe 20% or
>so), and see if it turns metallic.
>
>I then tried the base with 5% rutile only. Well, that was the plan, anyway.
>I apparently didn't wash out the container very well, though, because my
>rutile base ended up a very pretty, pale purplish blue. It seems more
purple
>under fluorescent lights (and outside) than under incandescent.
>
>It's hard to believe such a small amount of cobalt carbonate could impart
>this much color to a 500 gram test batch. Well, I'm still learning. That's
>what I get for being sloppy, huh?
>
>That little boo-boo might turn out to be a rather nice glaze, but it did
>kind of mess up my subsequent tests, which were for layering, so I won't go
>into those. I'll try them again later.
>
>I found a recipe for green which looked similar to my Opal Blue base. Also,
>Chris suggested that she'd read about cobalt greens prospering in
>high-alumina environments. I altered the green recipe slightly (decreased
>the EPK) to the following, which Chris had also suggested:
>
>Opal Green/Blue
>
>EPK KAOLIN.......... 30.00 27.78%
> FRIT 3134........... 50.00 46.30%
> SILICA.............. 20.00 18.52%
> RUTILE.............. 5.00 4.63%
>*Cobalt Carbonate.... 3.00 2.78%
> ========
> 108.00
>
> CaO 0.68* 10.02%
> MgO 0.00* 0.03%
> K2O 0.00* 0.10%
> Na2O 0.31* 5.13%
> TiO2 0.24 5.00%
> ZrO2 0.00 0.05%
> Al2O3 0.42 11.25%
> B2O3 0.63 11.46%
> P2O5 0.00 0.07%
> SiO2 3.58 56.65%
> Fe2O3 0.01 0.24%
>
> Cost/kg 2.41
> Si:Al 8.54
> SiB:Al 10.04
> Expan 7.30
>
>The first test, I ran straight, as listed above. It came out with a lovely
>blue-green ground, with thicker areas similar to Opal Blue, only slightly
>lighter.
>
>The second test, I added 5% alumina. It came out uniformly, and very nicely
>textured blue-green. Thick areas were quite dark.
>
>The third test, I added another 5% alumina, for a total of 10%. It turned
>out a rather unremarkable brownish black with hard-to-see blue highlights.
I
> liked the first one best, but my daughter liked the second one.
>
>So, that's the story on Opal Blue and Green so far.
>
>Cindy Strnad
>Earthen Vessels Pottery
>RR 1, Box 51
>Custer, SD 57730
>USA
>earthenv@gwtc.net
>http://www.earthenvesselssd.com
>
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